Single- and Mixed-Phase TiO2 Powders Prepared by Excess-Hydrolysis of a Titanium Alkoxide

TL;DR

This study investigates how different water-to-titanium alkoxide ratios affect the phase composition, porosity, and crystallization behavior of TiO2 powders prepared by excess-hydrolysis, revealing distinct properties based on hydrolysis conditions.

Contribution

It provides a comparative analysis of TiO2 powders synthesized via excess-hydrolysis at different water ratios, highlighting the influence on phase, porosity, and crystallization.

Findings

Near-complete hydrolysis yields brookite and anatase phases.

High porosity and amorphous structure in organic-rich medium.

Phase transformation from anatase to rutile begins below 500°C.

Abstract

To investigate excess-hydrolysis of titanium alkoxides, TiO2 powders were fabricated from titanium-tetra-isopropoxide using 6:1 and 100:1 H2O:Ti (r) ratios. Powders were dried and fired at a range of temperatures ( up to 800 C). Hydroxylation and organic content in powders were characterised using ATR-FTIR, laser Raman microspectroscopy, and elemental microanalysis; surface area and pore size distribution were evaluated using N2 gas adsorption; phase composition was analysed using XRD and laser Raman microspectroscopy; and crystallite size was evaluated by XRD, TEM and SEM. Results showed near-complete hydrolysis in a predominantly aqueous medium (r = 100), resulting in precipitated crystalline powders exhibiting brookite and anatase, which begin to transform to rutile below 500 C. Powders precipitated in a predominantly organic medium (r = 6) underwent partial hydrolysis, were highly porous and exhibited an amorphous structure, with crystallisation of anatase occurring at 300 C and transformation to rutile beginning at 500 to 600C.